CN104953059B

CN104953059B - Support structure for battery unit in traction battery assembly

Info

Publication number: CN104953059B
Application number: CN201510148876.5A
Authority: CN
Inventors: 布莱恩·尤特利; 帕特里克·丹尼尔·玛古尔
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2014-03-31
Filing date: 2015-03-31
Publication date: 2020-03-10
Anticipated expiration: 2035-03-31
Also published as: DE102015104620A1; CN104953059A; US10090494B2; US20150280184A1

Abstract

The invention relates to a support structure for a battery cell in a traction battery assembly. A traction battery assembly may include an array of battery cells having opposing end faces, opposing side faces, and a bottom face. The traction battery assembly may further include a pair of end plates and a pair of side plates arranged to form a four-sided enclosure around the end faces and the side faces and configured to compress and hold the battery cells rather than being mechanically connected to the battery cells or covering the bottom face. The side plate may partially cover an upper portion of the battery cell array. The side panel has a lower horizontal edge, an upper horizontal edge, and at least one diagonal reinforcing rib configured to extend upwardly from a location where the vertical edge portion contacts the lower horizontal edge to the upper horizontal edge.

Description

Support structure for battery unit in traction battery assembly

Technical Field

The present disclosure relates to a thermal management system for a high voltage battery used in a vehicle.

Background

Vehicles, such as Battery Electric Vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), Mild Hybrid Electric Vehicles (MHEVs), or Full Hybrid Electric Vehicles (FHEVs), include traction batteries, such as High Voltage (HV) batteries, to serve as a source of propulsion for the vehicle. The HV battery may include components and systems that assist in managing vehicle performance and operation. The HV battery may include one or more arrays of battery cells electrically connected to each other between the battery cell terminals and the interconnector bus bars. The HV battery and ambient environment may include a thermal management system that assists in managing the temperature of the HV battery assembly, system, and individual battery cells.

Disclosure of Invention

A traction battery assembly includes an array of battery cells having opposing end faces, opposing side faces, and a bottom face. The traction battery assembly further includes a pair of end plates and a pair of side plates arranged to form a four-sided enclosure around the end faces and the side faces and configured to compress and hold the battery cells without mechanically attaching to the battery cells or covering the bottom face. The side plate partially covers an upper portion of the battery cell array. Each of the end panels and the side panels may have a pair of vertical edge portions and may be mechanically fastened to each other at the respective edge portions. The side plates may define a plane and the at least one mechanical fastener may be oriented substantially perpendicular to the plane. The side panel may have a lower horizontal edge, an upper horizontal edge, and at least one oblique reinforcing rib configured to extend upward from a position where the vertical edge portion intersects the lower horizontal edge to the upper horizontal edge. The middle plate may be located at the center of the battery cell array, mechanically fastened to the side plates, and configured to receive a bending moment force generated by the side plates. A plurality of spacers may be positioned between adjacent battery cells and include tabs extending from upper portions of the spacers configured to position and mate with bus bar modules extending between opposing end faces of the battery cell array. Each of the end plates may define a vertically oriented lift hole in an upper portion of the end plate, the lift hole configured to be grasped by an installation tool.

A vehicle includes an array of battery cells having opposing end faces, opposing side faces, a bottom face, and a top face. The vehicle further includes a pair of end panels corresponding to the opposing end faces and a pair of side panels corresponding to the opposing side faces. The end plates and the side plates are configured to compress and hold the battery cell array between the end plates and the side plates instead of being mechanically fastened to the battery cell array. The vehicle also includes a plurality of spacers, each spacer positioned between adjacent battery cells and including a tab projecting above the top surface, the tab configured to position and mate with the bus bar module, and each spacer defining a lower ridge configured to contact and support the adjacent battery cells at a portion of the battery cells above the bottom surface. Each spacer may further define an upper ridge configured to contact the adjacent battery cell at a portion of the battery cell below the top surface such that the lower ridge and the upper ridge hold the battery cell in a vertical direction. The side plate may define an upper portion configured to cover a portion of a top surface of the battery cell and a vertically-oriented receiving hole at either end of the upper portion, the receiving hole configured to receive a mechanical fastener and form (develop) a load between the side plate and the battery cell resulting from compression of the mechanical fastener. A pair of dielectric rails may be located between an upper portion of the side plates and the top surface of the battery cell array and may have a thickness such that a force is generated between the bottom surface and a surface below the bottom surface. The dielectric track may have a thickness at a mid-span of the dielectric track that is greater than a thickness at opposite ends of the dielectric track. The surface may be an upper portion of the thermal plate in thermal communication with the array of battery cells. The middle plate may be centrally located in the battery cell array, mechanically fastened to the side plates, configured to receive a force generated by a bending moment of the side plates, and define a vertical lifting hole at an upper portion of the middle plate configured to be grasped by a tool.

A traction battery assembly includes an array of battery cells having opposing end faces, opposing side faces, a top face, and a bottom face that define an enclosure. The traction battery assembly also includes a thermal plate in thermal communication with the battery cell and configured to direct a flow of a thermal fluid therein. The traction battery assembly also includes a four-sided support structure located outside of the enclosure, the support structure including opposing end plates and opposing side plates configured to compress and retain the battery cell between the end plates and the side plates rather than being mechanically fastened to the battery cell. The side panel includes an upper portion covering and extending along a portion of the top surface such that the upper portion and the hot plate generate vertical forces that press against the top and bottom surfaces, respectively. A plurality of spacers may be located between adjacent battery cells and define upper and lower ridges configured to contact and hold upper and lower edges of the battery cells therebetween, respectively. The end plates and the side plates may define connection holes oriented substantially parallel to a length direction of the battery cells and located at four corners of the support structure outside the package, and the connection holes may be configured to receive fasteners to mechanically connect the end plates and the side plates to each other. The end plates and the side plates may define connection holes oriented substantially parallel to a height direction of the battery cells and located at four corners of the support structure outside the package, and the connection holes may be configured to receive fasteners to mechanically connect the end plates and the side plates to each other. The side plates may at least partially contact respective opposite sides of the battery cell array. The middle plate may be located at the center of the battery cell array and connected to a substantially central portion of each side plate, and the middle plate may be configured to transfer a pressing force applied to the battery cell array. The side plates may define at least one oblique reinforcing rib extending from a lower horizontal edge of the side plates to a location on an upper portion of the side plates substantially equidistant from the end plates and the middle plate.

Drawings

Fig. 1 is a schematic diagram of a battery electric vehicle.

FIG. 2 is a perspective view of a portion of a thermal management system for the traction battery of the vehicle of FIG. 1.

Fig. 3 is a perspective view of a portion of a traction battery assembly.

Fig. 4A is a perspective view of a portion of another traction battery assembly including a battery assembly having an outer support structure and an array of battery cells.

Fig. 4B is a perspective view of a battery cell array of the battery assembly of fig. 4A.

Fig. 5 is a perspective view of an end plate of the battery assembly of fig. 4A.

Fig. 6 is a perspective view of a side plate of the battery assembly of fig. 4A.

Fig. 7 is a perspective view of a middle plate of the battery assembly of fig. 4A.

Fig. 8 is a perspective view of a spacer of the battery assembly of fig. 4A.

Fig. 9 is a perspective view of a battery cell of the battery assembly of fig. 4A.

Fig. 10 is a side view of the spacer and two battery cells of fig. 8.

Fig. 11 is a perspective view of a dielectric rail of the battery assembly of fig. 4A.

Fig. 12 is a perspective view of a portion of yet another traction battery assembly including a plurality of battery assemblies having an outer support structure and an array of battery cells.

Detailed Description

Embodiments of the present disclosure are described herein. However, it is to be understood that the disclosed embodiments are merely exemplary and that other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As one of ordinary skill in the art will appreciate, a number of the features illustrated and described with reference to any one of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combination of features shown provides a representative embodiment for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations.

FIG. 1 depicts a schematic diagram of a typical plug-in hybrid electric vehicle (PHEV). A typical plug-in hybrid electric vehicle 12 may include one or more electric machines 14 mechanically connected to a hybrid transmission 16. The electric machine 14 can operate as a motor or a generator. Furthermore, the hybrid transmission 16 is mechanically connected to the engine 18. The hybrid transmission 16 is also mechanically connected to a drive shaft 20, the drive shaft 20 being mechanically connected to wheels 22. The electric machine 14 is capable of providing propulsion and retarding capabilities when the engine 18 is turned on or off. The electric machine 14 also functions as a generator and can provide fuel economy benefits by recovering energy that would normally be lost as heat in a friction braking system. The electric machine 14 may also reduce pollutant emissions because the hybrid electric vehicle 12 may be operated in an electric mode or a hybrid mode under certain conditions to reduce the overall fuel consumption of the vehicle 12.

A traction battery or battery pack (battery pack)24 stores and provides energy that may be used by the motor 14. The traction battery 24 typically provides a high voltage Direct Current (DC) output from one or more arrays of battery cells (sometimes referred to as a battery cell stack) in the traction battery 24. The battery cell array may include one or more battery cells. The traction battery 24 is electrically connected to one or more power electronics modules 26 through one or more contactors (not shown). The one or more contactors isolate the traction battery 24 from other components when open and connect the traction battery 24 to other components when closed. The power electronics module 26 is also electrically connected to the electric machine 14 and provides the ability to transfer electrical energy bi-directionally between the traction battery 24 and the electric machine 14. For example, a typical traction battery 24 may provide a DC voltage, while the electric machine 14 may require a three-phase Alternating Current (AC) voltage to operate. The power electronics module 26 may convert the DC voltage to a three-phase AC voltage required by the motor 14. In the regeneration mode, the power electronics module 26 may convert the three-phase AC voltage from the electric machine 14 acting as a generator to the DC voltage required by the traction battery 24. The description herein applies equally to electric only vehicles. For an electric-only vehicle, the hybrid transmission 16 may be a gearbox connected to the electric machine 14 and the engine 18 may not be present.

The traction battery 24 may provide energy for other vehicle electrical systems in addition to providing energy for propulsion. A typical system may include a DC/DC converter module 28 that converts the high voltage DC output of the traction battery 24 to a low voltage DC supply that is compatible with other vehicle loads. Other high voltage loads (e.g., compressors and electric heaters) may be connected directly to the high voltage without using the DC/DC converter module 28. In a typical vehicle, the low voltage system is electrically connected to an auxiliary battery 30 (e.g., a 12V battery).

A Battery Electric Control Module (BECM)33 may be in communication with the traction battery 24. The BECM33 may serve as a controller for the traction battery 24, and may also include an electronic monitoring system that manages the temperature and state of charge of each battery cell. The traction battery 24 may have a temperature sensor 31, such as a thermistor or other temperature gauge. The temperature sensor 31 may communicate with the BECM33 to provide temperature data regarding the traction battery 24. The temperature sensor 31 may also be located on or near a battery cell in the traction battery 24. It is also contemplated that more than one temperature sensor 31 may be used to monitor the temperature of the battery cells.

For example, the vehicle 12 may be an electric vehicle (e.g., a PHEV, FHEV, MHEV, or BEV) in which the traction battery 24 may be recharged by the external power source 36. The external power source 36 may be connected to an electrical outlet. The external power source 36 may be electrically connected to an electric vehicle charging equipment (EVSE) 38. The EVSE 38 may provide circuitry and control to regulate and manage the transfer of electrical energy between the power source 36 and the vehicle 12. The external power source 36 may provide DC power or AC power to the EVSE 38. The EVSE 38 may have a charging connector 40 for plugging into the charging port 34 of the vehicle 12. The charging port 34 may be any type of port configured to transmit electrical power from the EVSE 38 to the vehicle 12. The charging port 34 may be electrically connected to a charger or an onboard power conversion module 32. The power conversion module 32 may regulate the power supplied from the EVSE 38 to provide the appropriate voltage and current levels to the traction battery 24. The power conversion module 32 may cooperate with the EVSE 38 to coordinate the transfer of power to the vehicle 12. The EVSE connector 40 may have prongs that mate with corresponding recesses of the charging port 34.

The various components discussed may have one or more associated controllers that control and monitor the operation of the components. The controllers may communicate via a serial bus, such as a Controller Area Network (CAN), or via discrete conductors.

A battery cell (e.g., a prismatic battery cell) may include an electrochemical cell that converts stored chemical energy into electrical energy. Prismatic cells may include a housing, a positive electrode (cathode), and a negative electrode (anode). The electrolyte may allow ions to move between the anode and cathode during discharge and then return during recharge. The terminals may allow current to flow from the battery cells for use by the vehicle. When multiple battery cells are held in an array, the terminals of each battery cell may be aligned with opposing terminals (positive and negative) adjacent to each other, and the bus bars may assist in facilitating a series connection between the multiple battery cells. The cells may also be arranged in parallel so that the same terminals (positive and positive or negative and negative) are adjacent to each other. For example, two battery cells may be arranged with positive terminals adjacent to each other, and the next two battery cells may be arranged with negative terminals adjacent to each other. In this example, the bus bar may contact the terminals of all four battery cells.

The traction battery 24 may be heated and/or cooled using a liquid thermal management system, an air thermal management system, or other methods known in the art. Referring now to fig. 2, in one example of a liquid thermal management system, the traction battery 24 may include an array of battery cells 88, the array of battery cells 88 being shown supported by a thermal plate 90 to be heated and/or cooled by the thermal management system. The battery cell array 88 may include a plurality of battery cells 92 and structural components held adjacent to one another. Under certain operating conditions, the DC/DC converter module 28 and/or the BECM33 may also require cooling and/or heating. The thermal plate 91 may support and assist in thermal management of the DC/DC converter module 28 and the BECM 33. For example, the DC/DC converter module 28 may generate heat that may need to be dissipated during voltage conversion. Alternatively,

platens

90 and 91 may be in fluid communication with each other to share a common fluid inlet port and a common outlet port.

In one example, the battery cell array 88 may be mounted to the thermal plate 90 such that only one surface (e.g., bottom surface) of each battery cell 92 contacts the thermal plate 90. The thermal plate 90 and each battery cell 92 may transfer heat between each other to assist in managing thermal conditions (thermal conditioning) of the battery cells 92 in the battery cell array 88 during vehicle operation. In order to provide effective thermal management of the battery cells 92 and other surrounding components in the battery cell array 88, uniform thermal fluid distribution and high heat transfer capability are two considerations for the thermal plate 90. Since heat is transferred between the thermal plate 90 and the thermal fluid via conduction and convection, the surface area of the thermal fluid flow field is important for efficient heat transfer (both removing heat and heating the battery cells 92 at low temperatures). For example, the performance and life of the battery cell array 88 may be negatively affected if the heat generated by charging and discharging the battery cells is not removed. Alternatively, the thermal plate 90 may also provide heat to the battery cell array 88 when the battery cell array 88 is subjected to low temperatures.

Platen 90 may include one or more channels 93 and/or cavities to distribute the thermal fluid through platen 90. For example, platen 90 may include an inlet 94 and an outlet 96 that may be in communication with channels 93 to provide and circulate a thermal fluid. The location of inlet port 94 and outlet port 96 relative to battery cell array 88 may vary. For example, as shown in fig. 2, inlet port 94 and outlet port 96 may be centrally located with respect to cell array 88. Inlet port 94 and outlet port 96 may also be located at the sides of battery cell array 88. Alternatively, platens 90 may define a cavity (not shown) in communication with inlet 94 and outlet 96 for providing and circulating a thermal fluid. Platen 91 may include an inlet port 95 and an outlet port 97 to deliver and remove hot fluid. Alternatively, a plate of thermal interface material (not shown) may be applied to thermal plate 90 under battery cell array 88 and/or thermal plate 91 under DC/DC converter module 28 and BECM 33. The thermal interface material plate may enhance heat transfer between battery cell array 88 and thermal plate 90 by filling voids and/or air gaps between battery cells 92 and thermal plate 90, for example. The thermal interface material may also provide electrical insulation between the battery cell array 88 and the thermal plate 90. Battery tray 98 may support thermal plates 90, thermal plates 91, battery cell array 88, and other components. The battery tray 98 may include one or more recesses for receiving the thermal plate.

Various vehicle variables, including packaging constraints and power requirements, may be handled using different battery pack configurations. The battery cell array 88 may be housed in a casing or housing (not shown) to protect and enclose the battery cell array 88 and other surrounding components (e.g., the DC/DC converter module 28 and the BECM 33). The battery cell array 88 may be located in a number of different locations including, for example, under the front seat, under the rear seat, or behind the rear seat of the vehicle. However, it is contemplated that the battery cell array 88 may be located in any suitable location in the vehicle 12.

Fig. 3 shows an example of a portion of a traction battery, including a battery assembly 99 having two transverse end plates 100 and two longitudinal side rail assemblies 102. The battery cell array 104 is located between the transverse end plate 100 and the longitudinal side rail assembly 102. Each of the transverse end plates 100 includes four holes (not visible in this view) for receiving four fasteners (not shown) oriented substantially parallel to the longitudinal axis of the battery cell array 104. Each of the longitudinal side rail assemblies 102 includes four holes 106 aligned with the four holes of the transverse end plate 100 to receive the four fasteners so that the transverse end plate 100 is matable with the longitudinal side rail assemblies 102. Each of the transverse end plates 100 includes a lift boss (lift boss)108, the lift boss 108 including an axis 109 that is generally parallel to the longitudinal axis of the battery cell array 104. The lifting bosses 108 provide a location for tooling during assembly and/or installation configured to grasp (grapp) the battery assembly. In this example, the positioning and orientation of the lifting boss 108 requires the tool to grasp in a direction parallel to the axis 109 of the lifting boss 108 and at a location approximately half the height of the battery assembly 99. Each of the longitudinal side rail assemblies 102 includes three posts 110 spaced apart from the battery cell array 104. The side rail assembly 102 includes a lower portion that extends below the battery cell array 104 and contacts the battery cell array 104, and the lower portion is configured to assist in supporting the battery cell array 104. This battery assembly 99 is intended for an air-cooled thermal management system. In this way, the space between the post 110 and the battery cell array 104 provides a channel for air flow. The configuration of the lateral end plates 100 and side rail assemblies 102 requires additional packaging space and additional assembly space on the vehicle due to tool access to the wiring, which may not be desirable in a thermal management system for the traction battery. Additionally, the side rail assembly 102 extends beneath the battery cell array 104 to support and cover the bottom of the battery cell array 104, which may be undesirable in liquid-cooled thermal management systems because contact of the battery cells with the thermal plate is a factor that assists in providing efficient heat transfer between the two.

Fig. 4A-7 illustrate a portion of a traction battery assembly. Battery assembly 140 may include an outer support structure 142, with outer support structure 142 being configured to hold and support a battery cell array 144 including a plurality of battery cells 146 rather than being mechanically fastened to battery cell array 144. Outer support structure 142 may form a four-sided enclosure for battery cell array 144 and may be used for multiple battery cell array 144 embodiments, as described further below. Cell array 144 can have a bottom surface 145, opposing end surfaces 147, opposing side surfaces 148, and a top surface 149. The outer support structure 142 may include end plates 150 and side plates 152, with the end plates 150 and side plates 152 optionally not covering or contacting the bottom surface 145.

End plate 150 may define one or more positioning holes 154, one or more vertically oriented lifting holes 156, and one or more connecting

holes

158 or 159 to assist in assembling and mounting battery assembly 140. For example, the alignment apertures 154 may correspond to various alignment features and/or attachment points on the mounting surface of the battery assembly 140. The lift holes 156 may be located on an upper portion of the end plate 150 and may be configured to be grasped by a tool during assembly, installation, and/or transport, for example. In this way, the tool can be lowered (lower) from above the battery assembly 140 without the need to access the end plate 150 from the side. Such an access path may reduce the amount of assembly and/or installation space required for tool operation. In addition, since the side plates 152 are close to the side surfaces 148 of the battery cell array 144, the packaging space of the battery assembly 140 may be reduced. The axes of connection holes 158 may be oriented substantially parallel to the direction of the length of battery cell 146 and located at or near the four corners of outer support structure 142. These connecting holes 158 may be configured to receive fasteners 160 to assist in mechanically connecting the end plate 150 and the side plate 152 at the vertical edges of the end plate 150 and the side plate 152. The axis of the connection aperture 158 may also be substantially perpendicular to the plane defined by the side plate 152. The connection holes 158 may also be located outside of the package defined by the battery cell array 144. The axes of the connection holes 159 may be oriented substantially parallel to the direction of the height of the battery cells 146 and located at or near four corners of the outer support structure 142. These connection holes 159 may be configured to receive fasteners 161.

End plate 150 may correspond to end surface 147 and may be configured to receive clamping compression loads and other loads directed and transferred to end surface 147 of battery cell array 144. These loads may cause the battery cell array 144 to twist and bend during installation of the battery assembly 140, for example.

The plurality of spaced apart cut-outs 164 may be at least partially defined by angled ribs 166 of the side plates 152. The cut-out 164 may have different shapes including the examples shown in fig. 4 and 6. The side panels 152 may also define a lower horizontal edge 170 and an upper horizontal edge 172. Side plates 152 may partially contact sides 148 of battery cell array 144 or may not directly contact sides 148. The diagonal ribs 166 may extend at approximately a forty-five degree angle from the lower and upper

horizontal edges

170, 172 and may provide additional rigidity to the outer support structure 142. It is also contemplated that the angled ribs 166 extend at an angle other than forty-five degrees. In one example, one or more diagonal ribs 166 may extend from a location near or intersecting a vertical edge of each end plate 150 with a lower horizontal edge 170 of each side plate 152.

The middle plate 180 may be located in the center of the battery cell array 144 and mechanically fastened to the side plates 152. Intermediate plate 180 may provide additional structural rigidity to outer support structure 142. For example, it may be desirable to include the intermediate plate 180 when the length of the battery cell array 144 is such that the structural integrity of the battery assembly 140 may be compromised upon application of a certain force. As described above, the assembly and/or installation process may include applying a force to the battery assembly 140. The intermediate plate 180 may be configured to withstand and/or transfer forces generated by bending loads on the side plates 152 and/or compressive forces applied to the battery cell array 144. The middle plate 180 may define a vertical lift hole 182 in an upper portion of the middle plate 180, and the lift hole 182 may be configured to be grasped by a tool. The middle plate 180 may also be configured to be coupled to a support structure, such as a cover of the battery assembly 140, above the battery cell array 144. The middle plate 180 may also define attachment holes 184, and the attachment holes 184 may be configured to receive fasteners to assist in mechanically fastening the middle plate 180 and the side plates 152. To further assist in providing rigidity to the battery assembly 140, the diagonal ribs 166 may extend from the lower horizontal edges 170 of the side plates 152 to a location on the upper horizontal edges 172 of the side plates 152 that is approximately equidistant from the end plates 150 and the intermediate plates 180.

Referring now additionally to fig. 8-10, a plurality of spacers 190 may be located between adjacent battery cells 146. The spacers 190 may be made of a material such as polypropylene and assist in providing a creepage and clearance distance between adjacent battery cells 146 and/or between battery cells 146 and end plates 150. Each spacer 190 may include a tab 192 extending from an upper portion of the spacer 190. The tabs 192 may be configured to assist in positioning components, such as bus bar modules (not shown), to connect the components to the battery assembly 140 or mate with the battery assembly 140. Spacers 190 may also define one or more upper ridges 194 and one or more lower ridges 196 that may assist in orienting and retaining battery cells 146 in outer support structure 142. Upper ridge 194 may contact and assist in supporting battery cell 146 and may be located at an upper edge of battery cell 146. The lower ridge 196 may contact and assist in supporting the battery cell 146 without interfering with mating contact between the bottom surface 145 defined by the array of battery cells 144 and a surface (e.g., a hot plate) below the bottom surface 145 or between the lower edge of the battery cell 146 and a surface below the lower edge.

Fig. 11 shows an example of a dielectric track 202. Battery assembly 140 may include one or more dielectric rails 202 located between an upper portion 204 of side plates 152 and a top surface 149 of battery cell array 144. The dielectric rail 202 may be composed of a resilient, insulating material (e.g., rubber) and has a thickness such that a force is generated between the bottom surface 145 of the battery cell array 144 and a surface below the bottom surface 145. One example of such a surface is a hot plate (not shown). The thickness of the dielectric rail 202 may be constant along the length of the dielectric rail 202 that may be in contact with the battery cell array 144. Alternatively, the thickness of the dielectric rail 202 may increase at the midspan of the dielectric rail 202 such that there is a greater interfering contact with the battery cell 146 at the midspan. This increase in thickness at the mid-span of the dielectric track 202 may be adjusted to compensate for the maximum bending deflection possible at the mid-span of the dielectric track 202. Any increase in thickness of the dielectric rails 202 may be gradual or may include discontinuous steps. The interference thickness may be achieved by a series of downwardly upstanding ridges or nubbins that tend to have a minimum interference contact with the cell 146 near the end plate 150 and a maximum interference contact with the cell 146 at the mid-span of the dielectric rail 202. The dielectric rails 202 may also assist in electrically insulating the battery cells 146 from the side plates 152. Upper portion 204 of side plate 152 may cover a portion of top surface 149 of battery cell array 144 and extend along a portion of top surface 149 such that upper portion 204 and a surface (e.g., a hot plate) below battery cell array 144 may apply a vertical force to battery cell array 144.

Although fig. 9 illustrates one example of a battery cell 146, outer support structure 142 may also be used with other types of battery cells having different performance requirements and dimensional characteristics. For example, with respect to PHEVs and BEVs, the desired geometry and provided packaging space for each battery cell array may dictate battery cells having multiple configurations in multiple battery cell arrays. In these examples, the battery cell may be fourteen PHEV battery cells in an array of battery cells. For FHEV, the battery cell may be thirty FHEV battery cells in an array of battery cells. It may also be beneficial to have different types of battery cell arrays in the vehicle. For example, fig. 12 shows a portion of a traction battery assembly that includes a set of battery assemblies 250, a set of battery assemblies 250 having four battery cell arrays 252, four battery cell arrays 254, and two battery cell arrays 256. As shown, the end plates 258 and side plates 259 of each outer support structure holding a respective battery cell array may be modified to accommodate the particular battery cell array. The

battery cell arrays

252 and 254 may not require additional structural support, and therefore, the

battery cell arrays

252 and 254 do not include an intermediate plate. However, the battery cell array 256 is slightly longer than the

battery cell arrays

252 and 254, and thus, the battery cell array 256 may include an intermediate plate 260.

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously described, features of the various embodiments may be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments have been described as providing advantages or being preferred over other embodiments or over prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art will recognize that one or more features or characteristics may be compromised to achieve desired overall system attributes, depending on the particular application and implementation. These attributes may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, ease of maintenance, weight, manufacturability, ease of assembly, and the like. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the present disclosure and may be desirable for particular applications.

Claims

1. A traction battery assembly comprising:

an array of battery cells, each battery cell having an end face, a side face, and a bottom face;

a spacer disposed between the battery cells and including a lower ridge extending from the spacer to contact a portion between the side surface and the bottom surface of an adjacent battery cell such that the bottom surface is substantially flush with a hot plate disposed below the bottom surface;

a middle plate located at the center of the battery cell array and defining a thickness greater than the thickness of the spacer; and

a pair of end plates and a pair of side plates arranged to form a four-sided enclosure around the array of battery cells to compress the battery cells without using a mechanical connection and without covering the bottom surface,

wherein each of the side panels further comprises a lower horizontal edge, an upper horizontal edge, and at least one diagonal reinforcing rib having a portion at the lower horizontal edge or the upper horizontal edge adjacent an end of the middle panel and adjacent the side panel secured to the middle panel,

wherein each of the pair of end plates defines a vertically oriented lift hole in an upper portion of the end plate, the lift holes configured to be grasped by an installation tool.

2. The traction battery assembly of claim 1, wherein each of the end plates and the side plates has a pair of vertical edge portions and are mechanically fastened to each other at the respective edge portions by mechanical fasteners.

3. The traction battery assembly of claim 2, wherein the side plates define a plane and at least one of the mechanical fasteners is oriented substantially perpendicular to the plane.

4. The traction battery assembly of claim 1, wherein the intermediate plate is mechanically fastened to the side plates and arranged with the end plates and side plates to withstand bending moment forces generated by the side plates.

5. The traction battery assembly of claim 1, wherein each of the spacers includes a tab projecting from an upper portion of the spacer, the tab configured to position and mate with a bus bar module extending between the end faces of the battery cell array.

6. The traction battery assembly of claim 1, wherein a vertically oriented further lifting hole is defined in an upper portion of the intermediate plate, the further lifting hole configured to be grasped by the installation tool.

7. A traction battery assembly comprising:

an array of battery cells, each battery cell having opposing major sides and a bottom surface contacting the thermal plate, wherein the major sides are sides of the battery cells having a largest area;

spacers disposed between the major sides, each spacer having a lower edge and defining a lower ridge contacting a thermal plate, the lower ridge extending downward from a central portion of the lower edge to contact a portion between the major side and the bottom of the corresponding battery cell, and a region of the lower edge where the lower ridge is not formed being spaced apart from the thermal plate;

a middle plate positioned at the center of the battery cell array;

a four-sided support structure including opposing end plates and opposing side plates configured to compress and hold the battery cell between the end plates and the side plates without being mechanically fastened to the battery cell,

8. The traction battery assembly of claim 7, wherein the bottom surfaces of the battery cells define an enclosure, wherein the four-sided support structure is located outside of the enclosure, and wherein the side plates include an upper portion that covers and extends along a portion of the top surface of each battery cell such that the upper portion and the thermal plate generate a vertical force that presses against the top and bottom surfaces, respectively.

9. The traction battery assembly of claim 8, wherein the end plates and side plates each define connection holes oriented substantially parallel to a length direction of the battery cell and located at four corners of the support structure outside of the enclosure, and the connection holes are configured to receive fasteners to mechanically connect the end plates and side plates to each other.

10. The traction battery assembly of claim 8, wherein the end plates and side plates each define connection holes oriented substantially parallel to a height direction of the battery cell and located at four corners of the support structure outside the enclosure, and the connection holes are configured to receive fasteners to mechanically connect the end plates and side plates to each other.

11. The traction battery assembly of claim 8, wherein the side plates at least partially contact respective opposing sides of the battery cells outside of the battery cell array.

12. The traction battery assembly of claim 8, wherein the intermediate plate is connected to a substantially central portion of each side plate and is configured to transfer compressive forces applied to the battery cell array.

13. The traction battery assembly of claim 8, wherein the side plates each define at least one oblique reinforcing rib extending from a lower horizontal edge of the side plate to a location on an upper portion of the side plate substantially equidistant from the end plates and the intermediate plate.